Development of 2.5D and 3D IC Fabrication and Assembly Technologies

2.5D/3D IC assembly is where the traditional foundry and assembly house model breaks down. The greatly reduced feature sizes of microbumps in combination with very large, thin interposers and ICs present many challenges for assembly. With densely integrated packages and stacked thin dies, warpage at various steps of assembly process can lead to die crack, weak or open interconnection, and delamination. Microbump die with copper pillar and solder cap lacks the flexibility of conventional BGA solder balls in warpage compensation. Low temperature dielectric materials for interposer backside passivation lack chemical, thermal stability and mechanical strength compared to similar materials cured at higher temperatures. Ultra- low stand-off between dies creates new challenge for flux residue removal and underfill processing, adhesion and reliability. In this paper, we present learning and results from building two Invensas 2.5D interposer test vehicles with rectangular (19mmx27mm) and square (24mmx24 mm) silico...